1. Field of the Invention
This invention relates to method and apparatus employing UV energy for sealing articles in plastic packages, each package comprising a first piece with a peripherally extending groove and a second plastic piece with a peripheral portion designed to nest within the first piece.
2. Description of the Prior Art
One popular method for packaging articles in transparent plastic involves the use of the blister package, the package comprising a transparent blister piece and a backing sheet of foil or paper which is sealed to the blister piece after the blister piece is filled with the article to be packaged. To a large extent the task of sealing blister packages was met by the use of heat curable adhesives and sealing equipment designed for thermobonding such packages. An example of thermo sealing packaging devices is shown in U.S. Pat. No. 3,686,059. These processes, all of which involved the application of heat, were an improvement over earlier developments, yet they also carried many drawbacks which has led to the development of packaging machines for blister packages which utilize ultraviolet curable adhesive and the manipulation of UV radiation.
The state of modern packaging design has now evolved beyond the blister pack to the clamshell package which offers advantages including consumer appeal, recyclability and versatility. The so-called clamshell package is constructed differently to the blister package and uses two clear plastic shells that are shaped to nest with each other. In response to the need for means for sealing clamshell packages, systems have been developed using ultrasonic techniques, radio frequency (r.f.) energy, and heat curable glue. These systems all carry drawbacks, however. In addition, the known U.V. systems for the blister pack design are clearly not adapted for the differently structured clamshell packages. It is further noted that the available packaging systems appear to be primarily designed to address mass production requirements and entail relatively high acquisition and operating expenses. The available equipment has not met the requirements of many relatively small entities for an effective yet affordable way to seal clamshell packages.